1. Field of the Invention
The present invention relates to a fuel cell hose, and more particularly, it relates to a fuel cell hose that can be used as a hose for transporting pure water and a hydrogen hose for transporting hydrogen or steam-containing hydrogen, etc., which are used for a fuel cell system.
2. Description of Art
A power generation system using a fuel cell system (in particular a Proton Exchange Membrane fuel cell) has been highly expected as a future power generation system. However, it is said that the region for generating electricity in such a fuel cell system significantly deteriorates in its performance due to an external contaminant such as sulfur or a metal ion. For this reason, it is required that a hose to be used in a fuel cell system should have a low extractability, (i.e., a property that the material tends not to be extracted by water or the like flowing through a hose) and should be clean. Further, when a fuel cell system is used particularly for a vehicle, one of the important issues remaining is how to cool a great amount of heat generated thereby. Thus, it is said that the role taken by the cooling system is significantly important, however there is a concern that when the electrical conductivity of a coolant such as LLC (Long Life Coolant) increases, electrical short-circuiting may occur. Therefore, it is required for a hose to be used in a fuel cell system to maintain the insulation performance against internal fluid (water or LLC), in other words, to suppress ion extraction so as not to increase the electrical conductivity of the fluid.
Heretofore, under such circumstances, a stainless (SUS) tube has been used in many cases because of its low ion dissolution. However, when an SUS tube is used, it is difficult to mold the SUS tube or to compensate for any installation errors, which causes problems in terms of layout and assembly. In addition, SUS tubes have a problem of poor vibration durability and the like
For this reason, a resin hose in which a resin is used has been recently used for a fuel cell hose instead of conventional SUS tubes. For example, a hydrogen hose comprising an inner layer made of a material selected from a polypropylene (PP) resin, a polyethylene (PE) resin, an olefin thermoplastic elastomer (TPO), a fluorine-containing resin and a styrol resin, an intermediate layer made of an ethylene vinyl alcohol copolymer (EVOH), and an outer layer made of a polyamide resin has been proposed (see, for example, Japanese Unexamined Patent Publication No. 2002-213659 (Patent Document 1)).
However, the inner layer of the hydrogen hose described in the Patent Document 1 is made of a polypropylene (PP) resin or the like, therefore, the inner layer is hard and inferior in flexibility. Accordingly, when such a hose is cooled to a low temperature (about −40° C.) and bent to 180°, abnormalities such as cracking on an inner or outer surface of the hose may occur, i.e., the hose is inferior in low-temperature flexibility. Also, defects such as buckling or cracking may occur when a connector is press fitted to the hose. Further, when the inner layer of the hydrogen hose is made of the olefin thermoplastic elastomer (TPO), it is inferior in barrier performance against water or hydrogen gas. Further, there are disadvantages in that when the inner layer of the hydrogen hose is made of the fluorine-containing resin, it is inferior in barrier performance against hydrogen gas, and in particular when the inner layer is made of a soft fluorine-containing resin such as tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), it is also inferior in barrier performance against water.